Work coil for induction heating



Jan. 31, 1967 H. NEAL 3,301,990

WORK COIL FOR INDUCTION HEATING Filed Jan. 17, 1964 INVENTOR.

HERBERT NEAL BY waif AGENT United States Patent 3,301,990 WORK COIL FOR INDUCTION HEATING Herbert Neal, Ringwood, Victoria, Australia, assignor to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed Jan. 17, 1964, Ser. No. 338,448

Claims priority, application Australia, Jan 17, 1963,

13 Claims. (Cl. 21910.79)

This invention relates .to inductive heating devices comprising at least one rotary coil having a plurality of turns in the magnetic field of which an object may be heated wholly or in part by high-frequency energy. Such a device is generally known per se.

Known devices have the disadvantage that the heating of an object by an induction coil, wherein the object is located at a certain distance from the longitudinal axis thereof, is not uniform enough .even if, as reckoned in the longitudinal direction of the coil, the turns have a constant pitch and also a constant diameter. The heating will be much stronger near the individual turns than near the longitudinal axis of the coil.

The utility of the known heating device may be considerably improved if, according to the invention, the coil is made rotatable about its own longitudinal axis or about another axis extending in parallel with it. It has been found that, as reckonul over the length of the coil, the uniformity of heating at a certain distance from the longitudinal axis of the coil is greatly improved both inside and outside the diameter of the coil.

A heating device according to the invention may be used, for example, for heating the wall of a bore such as may be present, for example, in a metallic casting or forging where the wall of the here is required to be heated very uniformly. By using coils rotating about an axis of rotation extending in parallel with the longitudinal axis of the coil, and wherein the distance between the two axes is adjustable, it may be achieved that bores of different diameters can be treated with a coil of only one given diameter. By the choice of the rotary coil it is also rendered possible, for example, in bulk manufacturing processes, for a large number of small objects present on a conveyer belt to be exposed in succession to an identical thermal treatment with no need, for example, to stop the conveyor belt periodically for a short time. To this end, such an embodiment is characterized in that a conveyer for the objects, preferably arranged outside the coil, is designed to transport a number of objects in the longitudinal direction of the coil, thereby leaving the objects during their transport wholly or in part between adjacent turns of the coil. In such a device the space which exists directly between the material of adjacent turns and where the inductive heating is strongest is thus utilized most efficiently, This is also important, for example, for heating objects which cannot readily be introduced into a high-frequency coil because of their dimensions. However, if such objects are slim (or substantially flat) it is possible to bring them wholly or in part between the adjacent turns of a coil sideways and leave them in situ for some time. An inductoin heating technique of this type has the further advantage, for example, that temperature control on the transported, treated objects is possible, for example, by slightly varying the pitch of the turns in the same coil.

It is not necessary that the .turns of the coil be circular. Also it is not always necessary for all the turns to be wholly identical. One portion of the coil may have, for example, elliptical turns and another portion may have, for example, circular turns. The diameters of the various turns may differ greatly according to require- 3,301,990 Patented Jan. 31, 1967 ice ments and it is also possible that the pitch, as reckoned over the length of the coil, is not chosen constant in order to make the heating of the objects adjustable. Also the Whole of the coil may have, likewise, according to requirements, a shape which is, for example, conical.

In order that the invention may 'be readily carried into effect, a device for the high-frequency heating of objects during their transport will not be described in detail, by way of example, with reference to the accompanying diagrammatic drawing.

The figure shows an inductance coil 1 which is connected by means of couplings 3 and 5 to shafts 7 and 9. The shaft 9 is a driven shaft so that the coil 1 is rotatable about an axis which lies in line with the shaft 9. The coil 1 is connected through the shafts 7 and 9 to an electric circuit, This electric circuit and the manner in which the coil 1 is possibly cooled will not be described further in this specification.

A conveyor 15, which runs over Wheels 11 and 13', is arranged outside the coil 1 and designed so that objects 17 to be heated may be transported in their position shown in the direction indicated by arrow 19. The arrangement is synchronized with the angular velocity of the coil so that, during rotation of the coil, the objects can remain, at least in part, between adjacent turns of the coil during their transport.

In operation of the device the objects may thus be exposed during transport to intense heating in a field between the material of adjacent turns with no need for the objects to leave, for example, the conveyor belt in the meantime.

In this example reference is made especially to the high-frequency heating of objects 17 which are needleshaped or substantially fiat. By varying the pitch S of the turns it may be achieved, for example, that the degree of heating is adjustable in accordance with a special program.

In the present example the coil rotates about an axis of rotation extending in line with the shaft 9. If desired, the arrangement may be such that .the coil is rotated about an axis parallel to its own longitudinal axis. Thus, the heating zone of the objects 17 laterally inserted into the coil is extended and the energy imparted to the objects is distributed more satisfactorily.

In the embodiment described, the rotation of the coil was continuous. It will be evident that the invention is naturally also applicable to coils which are rotatable discontinuously. In this case the movement of the objects must, of course, also be discontinuous.

What is claimed is:

1. Apparatus for inductively heating one or more objects comprising, an induction heating coil having a plurality of turns and a longitudinal axis, means for supplying high-frequency electrical energy to said coil, means positioning said object to be heated adjacent said coil in operative relation to the magnetic field of the coil, means for rotating said coil about its longitudinal axis or about an axis parallel thereto, and conveyor means for moving said object to be heated in a direction parallel to said longitudinal axis of the coil, said conveyor means and said coil being arranged relative to one another so that during the transport of said object at least a portion of said object extends between adjacent turns of said coil.

2. Apparatus as described in claim 1 wherein said conveyor means is positioned outside of the coil.

3. Apparatus as described in claim 1 wherein said conveyor means is arranged to move said object or objects in synchronism with the rotation of said coil where by said objects lie wholly or in part between adjacent turns of thecoil during the transport thereof along the coil.

4. Apparatus for inductively heating an object comprising, an induction heating coil having a plurality of turns extending along its longitudinal axis, means for supplying high-frequency electrical energy to said coil, means positioning said object to be heated adjacent said coil in operative relation to the magnetic field of the coil, means for rotating said coil about said longitudinal axis, and means for moving said object in synchronism with the coil rotation in a direction parallel to said longitudinal axis and at a speed relative thereto such that at least a portion of said object extends between adjacent turns of said coil.

5. Apparatus as described in claim 4 wherein the pitch of the coil turns varies along at least a portion of said longitudinal axis.

6. Apparatus as described in claim 4 wherein the radii of different turns are unequal.

7. Apparatus as described in claim 6 wherein said coil is conically shaped.

8. Apparatus as rescribed in claim 4 wherein the shape of certain ones of the turns are different than certain other ones of the turns.

9. Apparatus for inductively heating an object comprising, an induction heating coil having a plurality of turns extending along its longitudinal axis, means for supplying high-frequency electrical energy to said coil, means positioning said object to be heated adjacent said coil in operative relation to the magnetic field of the coil, and means for rotating said coil about an axis parallel to and spaced apart from said longitudinal axis.

10. Apparatus as described in claim 9 further com-- prising means for moving said object in synchronism with the coil rotation in a direction parallel to said 10ngi-,

tudinal axis and ata speed relative thereto such that at least a portion of said object extends between adjacent turns of said coil.

11. Apparatus as described in claim 10 wherein the pitch of the coil turns varies along the longitudinal axis in accordance with a predetermined heating program for said object.

12. Apparatus as described in claim 10 wherein said rotating means is arranged to rotate said coil discontinuously and wherein said moving means is arranged to move said object discontinuously in synchronism with said rotating means.

13. Apparatus for inductively heating an object comprising, an induction heating coil having a plurality of turns extending along its longitudinal axis, means for supplying high-frequency electrical energy to said coil, means positioning said object to be heated adjacent said coil in operative relation to the magnetic field of the coil such that a part of said object extends between adjacent turns of said coil, and means for rotating said coil about said longitudinal axis.

References Cited by the Examiner UNITED STATES PATENTS 2,556,236 6/1951 Strickland 2l9l0.4l

2,722,589 11/1955 Marquardt 2l9-l0.69

2,853,588 9/1958 Brown 21910.69

FOREIGN PATENTS 1,001,165 8/ 1965 Great Britain.

: RICHARD M. WOOD, Primary Examiner.

ANTHONY BARTIS, Examiner.

L. H. BENDER, Assistant Examiner. 

9. APPARATUS FOR INDUCTIVELY HEATING AN OBJECT COMPRISING, AN INDUCTION HEATING COIL HAVING A PLURALITY OF TURNS EXTENDING ALONG ITS LONGITUDINAL AXIS, MEANS FOR SUPPLYING HIGH-FREQUENCY ELECTRICAL ENERGY TO SAID COIL, MEANS POSITIONING SAID OBJECT TO BE HEATED ADJACENT SAID COIL IN OPERATIVE RELATION TO THE MAGNETIC FIELD OF THE COIL, AND MEANS FOR ROTATING SAID COIL ABOUT AN AXIS PARALLEL TO AND SPACED APART FROM SAID LONGITUDINAL AXIS. 